How and when should I use 44.1 kHz and 48 kHz?

[jordini]

Hi everybody!

My name's Jordan and while I'm primarily a videographer, I've been learning more about audio and how important it is for video at school lately (I'm currently studying TV broadcast). I play guitar, keyboards, and a little ukulele, bass, and harmonica. I play guitar and bass and sing in my band and dabble in a little solo recording at home just for fun. In addition to being a full time student, I freelance as an editor (which includes doing voiceover work in some cases). Also, I must say I've really enjoyed browsing this forum and have learned a lot.

I do have some questions though; if some of you guys could help me out it'd be much appreciated . I just bought a AT2020 mic and an Inspire 1394 audio interface with which record instruments and voiceover and am really excited with the possibilities, but I'm still pretty new and inexperienced with audio in general

In school, I learned a bit about sample rates - such as how 44.1 kHz is what CDs and such use and how most editing programs are set for 48 kHz. Now correct me if I'm wrong, but you shouldn't ever mix sample rates in a video, right? (i.e. having a 48 kHz voiceover with a 44.1 kHz music track)...doing that can result with the sound getting out of sync, right?

By default, my Final Cut Pro editing program is set to 48 kHz; does that mean that any audio I bring into the program should also be 48 kHz or converted in 48 kHz? I just checked a project I'd been working on and it looks like most of the audio is 44.1 kHz, and it all works and syncs with no problem.

I've got a lot of questions, I know (and a lot more coming, I'm sure), but I'd really appreciate any advice! Thanks!

[tacman7]

With my software a project has to be running at one sample rate.

When I import a file the program changes it to the right sample rate.

Sound forge can play both 44.1 and 48k when they system is running at 48k but will not play either if the system is running at the higher rates. That was kind of a hassle running the higher rates, I couldn't listen to the final output till I changes the audio sample rate of my interface.

I've been running 48k for some time now, I think it adds a little something to the quality.

I tried higher rates but it puts too much strain on my equipment. I give up the extra quality for ease of workflow.

Some people swear by 44.1 all the way type of methodology.

When I export my finished mix I dither to take it down from 24 to 16 bits but I leave it at 48k then when I take the exported file into sound forge (my sort of mastering program) I compress it then save it as a wma which is 44.1.
The output I'm getting fits my needs.

Looking at your needs.

Some say you use 44.1k for music and 48k for video.

If it works for you then it's right.

[richiebee]

CD = 44.1Khz
DVD = 48Khz (and up).

[darrylm]

While recording at 44.1kHz will capture the frequencies within the human hearing range, there is an advantage to going higher due to the mathematics of the way the signal is reproduced.

(Geek mode stuff: Essentially, the highest frequency captured will be 1/2 of the sampling rate (Wikipedia article on sampling theory). However, the frequency response of what is captured ideally follows the mathematical sync function, sin(x)/x, which is not a linear response. Practically, hardware and software approximations are typically used to limit the effect of the sync function, so it shouldn't be quite as noticeable as it otherwise might have been (e.g. "oversampling" by the cd player, etc.). But generally speaking, the higher the sampling rate, the greater the linearity of the frequency response within the human hearing range and (theoretically) the better it sounds.)

One way to capture a high sampling rate while *possibly* avoiding issues surrounding dithering is to record at double the rate that you will use to distribute your audio. So, for example, if you will eventually be releasing your music on CD (44.1kHz), you could record at 88.2kHz. Halving the sampling rate is theoretically easier for software to do as it simply amounts to averaging between samples. It's hard to say what each particular piece of software will do, however, so it may not be all that much of an advantage.

If you have time, it may be worth trying several different sampling rates and seeing if you can tell the difference when it's bounced down to 44.1kHz (or whatever you'll be releasing the final product in). If you notice an improvement at one sampling rate over another, then go for it. One simple quote I remember from a mixing book I've got is: If it sounds good, it is good. :-)

Edit: With regard to video, I suppose it depends on what your software does with files recorded at different sampling and bit rates. Hopefully recent programs will be smart enough to convert files to what they need? I have no idea what FCP does. If your voiceover sounds like a contra-bass or a chipmunk, then I guess that's one way you'd have your answer (i.e. the sampling rates weren't converted). If they sound ok, then the software is most likely converting the rates for you.

[tacman7]

I've read that the (88.2 is twice 44.1 so makes cleaner conversion etc.) argument is really moot. It seemed logical to me because it's true in converting images to prevent loosing a lot of data in the conversion but I was told on other forums that it doesn't hold true for audio with todays software.

There's no dithering involved in SRC only in bit reduction.

[jordini]

Thanks for you help, everyone!

Another quick newb question...as you know, I recently bought an AT2020, but I also just found an AKG C535 EB lying around my house. Is it worth using (compared to my AT2020)? And if so, which mic should I use for what kind of purpose?

Thanks!

[garageband]

Jeez, what confusing answers. My turn. Moving between sample rate and bit depths is a nightmare. Don't do it if you can possibly avoid it.

If you have hardware or software that has a preference, go that way. You say you need 48k for video? Do everything in 48k. Everything I have can run at 48k/24 EXCEPT my Tonelab. How miserable....you have no idea how switching back and forth can make otherwise stable hardware and software misbehave.

On the mics; whatever works. Bear in mind there is always chemistry between whatever mic and whatever preamp.

[garageband]

I also love the fact that you play "a little ukulele".

[fortyseven]

CD = 44.1Khz
DVD = 48Khz (and up).

You could run an experiment to see if changing between 44.1Khz and 48Khz would cause sync problems however I would just stick with using 48Khz.

[pmars]

So I should not buy an AT2020USB for voice overs with FCP since it records at only 44.1 and since FCP uses 48 I would be looking for trouble. Which I definitely do not need!!!
This is getting more complicated by the second. I need to find a super clean sounding USB mic that works great with everything and I do not want a CO1U.
Any suggestions at around $100 ???

[MetalDave]

I didn't like the fact the you play a little Bass..... The Big ones really have alot better tone. Kudos on the little ukulele though!